The invention relates to a line camera for imaging object strips on photosensitive detector lines, having an objective producing a line image of an object strip, having a ray deflecting system situated at the site of the line image by means of which the line image is divided into adjacent image sections in such a manner that paths of the rays pertaining to adjacent image sections are directed into respective different directions in space, as well as having an optical relay system arranged optically behind each image section for imaging the respective image section on a respective separate detector line.
A line camera of this type is known from the German patent document DE-AS 21 06 268. A method is described a picture of an object by means of line-by-line imaging from a stable-position missile flying over the object. The missile carries a camera which images object strips of the object, specifically ground strips of the surface of the earth, by means of an objective, first in its focal plane, as a line image. At the site of this line image, a ray deflecting system is situated which is composed of two mirror strips which abut one another in the longitudinal direction of the line image and by means of which the line image is divided into two image sections. The paths of the rays which pertain to these two image sections are deflected into two different directions in space by the mirror strips which are oriented in a different manner. Two optical relay systems are optically arranged behind the ray deflecting system and are each assigned to one of the two image sections respectively. These optical relay systems each plot a line-shaped image of the respective image sections on their own separate detector.
This known line camera is obviously designed only for relatively small image angles and is to be operated predominantly in the visible spectral range. It is therefore an object of the invention to provide a line camera of the initially mentioned type which, at the same time, is suitable for a very large viewing angle range (for example, approximately 110.degree.) and for a full use in the infrared spectral range.
In the case of a very wide-angle take of ground strips, naturally very long line images will be created, and therefore correspondingly long detector lines would normally have to be used. Although these exist for the visible spectral range (according to the magnitude, 6,000 detector elements with an overall length of 6 cm), no sufficiently long detector lines are available yet for the infrared spectral range. In addition, problems exist when there is the attempt to take along line image by stringing together individual detector lines, because at points where the lines abut, losses of information will occur. The production of a long detector line for the infrared range by placing together several short detector lines while avoiding any gaps is very expensive.
However, also if a single, very long detector line were to be used, additional problems would occur in the infrared range which are a result of the fact that this detector line must be effectively shielded from any type of interference irradiation. For this purpose, an aperture is arranged in front of the detector line in the path of the rays which, like the whole housing containing the detector line and the aperture, must be cooled to temperatures that are as low as possible. This results in considerable additional expenditures with respect to equipment as well as in considerable additional operating costs.
According to the invention, the above-mentioned object is achieved by means of an arrangement wherein the total number of the optical relay systems is divided into at least two groups, each group being assigned to another direction in space, the optical relay systems of each individual group each imaging the image sections assigned to them in a common focal plane on their respective separate detector lines which are arranged above one another in the respective focal plane in a line directed in parallel to the line image, and one screen respectively being arranged between each detector line and the respective optical relay system assigned to it.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.